Discussion
Our result demonstrates that the incidence of adhesion at the secondary CS is minimal or nonexistent and use of adhesion barrier did not reduce skin-to-delivery time and the likelihood of intraoperative or postoperative complications at the secondary CS. However, use of adhesion barrier films at the primary CS associated with a higher incidence of postcesarean fever which potentially means increased risk of SSI.
Existing similar study [23]reported adhesion rates of 18% vs. 17% in use and nonuse of HA-CMC and 20% vs. 83% in use and nonuse of ORC, respectively, at the repeat CS [19]. Our data reported minimal adhesion rates which are obviously lower than existing data [23]. We believe that is reliable because we minimize the effect of confounding factors such as history of pelvic inflammatory disease, endometriosis, and open abdominal or laparoscopic pelvic surgery before the primary and the secondary operations. Second, operations were performed by three physicians with profound experience and had minimal blood loss during operation. Third, all CS were operated with the same techniques that reduce adhesion (e.g., rectus muscle approximation, closure of the bladder flap and peritoneum) [3, 4, 26-30]. There were also many proposed mechanisms to explain why adhesion formation following CS was less than laparotomyin nonpregnant woman: (a) greater tissue perfusion in pregnancy is associated with less tissue hypoxia; (b) the lower segment incision is covered by the bladder which is constantly being filled and emptied during the healing process and this movement disrupts fibrinous formation between the uterus and the bladder and between the lower segment and the anterior abdominal wall; (c) one single incision in the lower segment at CS is less than myomectomy which associated with more tissue handling; (d) less hematoma developed in the low transverse incision at CS; (e) rapid change inuterine size in the postoperative period disrupts adhesion formation. In fact, evidence in the literature suggests that the consequences of postoperative adhesion such as bowel obstruction, urinary tract injury, infertility, ectopic pregnancy, and chronic pain may be less following CS compared with gynecological surgery [31].
Reported studies of the HA-CMC barrier found no differences in the incidence of adhesion, skin-to-delivery time, and total operative time which were consistent with our result except for higher rates of postcesarean fever after the primary CS [22-24]. However, only one of them mentioned about postoperative complications and most CS were elective in this study [22]. To date, cases of chemical peritonitis (inflammation) associated with adhesion barrier following emergency CS have been reported in Japan [32, 33]. The mechanisms leading to chemical inflammation associated with adhesion barrier have not been clear but the hyaluronan-based membrane has been observed to be associated with an increased adhesion in an animal model of bacterial peritonitis [34, 35]. These studies implied postcesarean peritonitis in patients who received the adhesion barrier films was associated with wound classification which reflects the degree of contamination of the wound during operation. A recent study showed the percentage of class III and class IV in emergency CS was 22.3% and the metritis rates of patients who received the HA-CMC barrier with contaminated or dirty/infected wound was much higher than cases using 4% Icodextrin solution (32.0% vs. 10.3%, p =0.048) [36]. It was mentioned that contaminated or dirty/infected wound with placement of anti-adhesion films may form occlusive barrier that prevents omentum to absorb the microabscess and serve as a culture medium to nourish bacteria.
Our concern is that patients who used adhesion barrier at the primary CS had significantly higher rates of postcesarean fever and therefore it is an independent risk factor of postcesarean fever. So we performed interaction term analysis to examine the impact of SSI risk factors [37] and use of adhesion barrier on postcesarean fever. And we found the strongest risk factor for postcesarean fever is the use of anti-adhesion film during emergency CS (p=0.041) as well as in cases where women have labor before operation (p=0.054). We think that it is because at least half of the primary CS in our study were conducted in emergency or having labor before operation. Most of them (e.g., prolonged labor, fetal distress) had long duration of labor or membrane rupture and they also received more digital vaginal examinations before operation. Thus, a contaminated wound with anti-adhesion films means more chances of having SSI.
Based from our data, the incidence of adhesion at the secondary CS is minimal or nonexistent and use of adhesion barriers at primary CS don’t significantly reduce adhesion, shorten the time needed for neonate delivery, and improve surgical outcome at repeat CS. Furthermore, use of adhesion barrier films during emergency cases and when a woman has labor before operation is associated with a significantly higher risk of postcesarean fever which potentially means increased risk of SSI. Unlike our study, analysis of SSI risk factors and use of adhesion barrier has not been available previously. Collectively, our study adds new information regarding impact of adhesion barrier on postcesarean fever.
There was only one phase IV prospective trial that has reported the effectiveness of HA-CMC at the repeat CS but there is no prospective trial for safety of use in specific condition such asemergency operation or labor before operation. There is also no prospective trial reporting the effectiveness and safety of ORC. Prospective studies comparing the effectiveness and safety of all adhesion barriers extensively used in primary CS can help in evaluating the cost-effectiveness of these products and developing evidence-based decision-making.